The present invention relates, generally, to a light-diffusing film for use in a backlight unit of a thin film transistor-liquid crystal display (TFT-LCD), and more particularly, to a light-diffusing film for displays, which uniformly diffuses light transmitted from a light source lamp positioned at the lateral side or the back surface of a display device, thus realizing vivid and distinct display images.
Recently, LCDs have been applied not only to monitors for notebook computers but also to large monitors for desktop computers and to TV monitors. Accordingly, a backlight unit for use in a light source of such an LCD is increasingly required to have a large size and high luminance.
In the backlight unit, a light-diffusing sheet functions to diffuse light of a light source from either a lateral side or the back surface of a display device to the entire display screen, and also convert it into light able to uniformly move forward through refraction. As such, a backlight process is an indirect lighting process for enhancing brightness of a display screen in a manner such that light originated from the light source of a backlight unit mounted to the back surface of a display device is transferred to the opposite side through a light guide plate and then reflected from a reflection plate, such as a metal deposition plate or an opaque white plate, to allow the light to move forward. Thus, the backlight process is a light emission technique capable of overcoming the problems of a conventional front-light process. As for the backlight process, when the number of light sources of a backlight unit is increased to realize high image brightness, power consumption and heat generation rate are increased. However, maximum light efficiency should be realized using minimum power consumption. In this regard, techniques for transferring light from a light source to a liquid crystal operator using a light-diffusing sheet comprising a base sheet and a light-diffusing layer formed on at least one surface thereof are receiving attention. Accordingly, the light-diffusing sheet requires an efficient design of the light-diffusing layer formed on the base sheet and improvement of the functions thereof depending on such a design.
For instance, Korean Patent Application No. 2004-7016125 discloses a light-diffusing film comprising a transparent film and a light-diffusing layer as a resin film layer having fine surface roughness formed on at least one surface of the transparent film, in which the transparent film includes a thermoplastic resin having a substituted and/or unsubstituted imido group at a side chain thereof, and a thermoplastic resin having a substituted and/or unsubstituted phenyl group and nitrile group. In addition, Korean Patent Application No. 1996-38912 discloses a method of forming a transparent resin layer including organic particles on a transparent plastic sheet for high light efficiency and luminance improvement.
However, such conventional techniques suffer because they have difficulty in actually realizing high luminance and shielding of LCDs, that is, improved total light transmittance and high haze, through only the variation in a combination of the types of the resin and the sizes of the particles applicable in the light-diffusing layer.